Approaching the cattle pen will uncloak a nightkin selling "wind-brahmin," which are the tumbleweeds that are littering the pen. The origin of this nightkin is completely unknown. If asked for the charge, he will demand every cap owned. If stated that he is crazy, he will reply with: "Crazy with low prices on wind-brahmin." Whether or not the Courier has 10 caps or 10 million caps, that is considered the "low-price" of tumble weeds. Originally, if agreed without asking, he'll present a Stealth Boy. But with the game patch released July 7–8, 2011, the nightkin will no longer present a Stealth Boy if agreed with without asking, and will take all of the caps offered instead. If his offer is refused, he'll become immediately hostile. A Stealth Boy can be pickpocketed from the nightkin, or will be on his corpse after he is killed. Further interactions, such as insinuating that the tumbleweeds are not in fact "doggies," results in the nightkin becoming hostile. If a wind-brahmin is purchased, the nightkin can then be killed to collect the lost caps. Killing and/or any other form of interaction with the nightkin does not affect Karma. It should also be noted that just in front of the pen is a dead wastelander.

The nightkin in the cattle pen will not be visible because he will be wearing a Stealth Boy. When near him, he will deactivate his Stealth Boy and he will open dialogue.

The tumbleweeds in the northwest corner of the pen seem to be attracted to that point. If rolled away from the pen, they will slowly be attracted back. This is due to the direction of the wind, and if lifted over the fence they will continue on west.

xbox360pcps3 If you have spoken to the nightkin that is selling the tumbleweeds, and then decide to reload the save, he will not appear. Exiting the game and going to the main menu, or restarting your game will fix this, though this will lead him to spawning wherever you loaded (maybe on the other side of the map). This may also lead to him reappearing every time you restart. Upon spawning, he may become hostile to those around you (leaving you alone) and will start killing them. This could potentially be used to assassinate people of interest. It is also possible that he might appear later on, as if he followed you, to somewhere random.[verified]

xbox360ps3 If you kill the nightkin and come back a few days later, upon entering the pen you will hear the nightkin coming out of stealth but nothing will appear anywhere.[verified]

xbox360 When initiating dialog, if you accept the offer without asking how much, he will give you the Stealth Boy without taking any caps.[verified]